POV-Ray : Newsgroups : povray.newusers : How can I fix surface perfections on my render? : Re: How can I fix surface perfections on my render? Server Time
18 Sep 2021 06:20:29 EDT (-0400)
  Re: How can I fix surface perfections on my render?  
From: Cousin Ricky
Date: 9 May 2020 20:47:22
Message: <5eb74f1a$1@news.povray.org>
On 2020-05-09 7:43 PM (-4), circuit wrote:
> Hey all. Just started using POV-Ray with FreeCAD. I'm trying to render a solid
> assembly, and so far have had reasonable success. The issue I'm facing is that
> the output surface has a lot of imperfections around edges. You can see what I
> mean here:
> 
> https://i.imgur.com/jmSYFlA.png

Without seeing the whole scene description file, it's hard to say, but 
the "imperfections" in the image look like radiosity artifacts.  The 
setting Radiosity_Normal uses:
   count 200
   error_bound 0.3
   pretrace_end 0.01

Increasing count will always improve radiosity, but tweaking the other 
settings can often get the job done more efficiently.  A pretrace_end of 
0.01 seemed fine for POV-Ray 3.6, which is what the scene file was 
designed for; but if your POV-Ray installation is 3.7 or later, 0.01 is 
inadequate.  The rad_def.inc settings were not updated in the 3.7 update.

These settings are usually good enough in my experience:
   error_bound 0.5
   pretrace_end 2 / max (image_width, image_height)
   recursion_limit 2

If there are still artifacts, try changing pretrace_end to:
   pretrace_end 1 / max (image_width, image_height)

P.S. As long as your scene file starts with #version 3.6; and uses 
radiosity, all ambients on non-glowing objects should be set to zero. 
If your objects and textures have ambients individually applied, and 
none of your objects glow in the dark, this is easily done with 
global_settings { ambient_light 0 }.  If you do have glowing objects, 
you cannot change the global ambient_light; you must instead use 
#default { finish { ambient 0 } }, and delete or override any ambients 
on non-glowing objects and textures.


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